netdev - Re: Latest net-next from GIT panic

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Message-ID: <1505914658.29839.94.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Wed, 20 Sep 2017 06:37:38 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Paweł Staszewski <pstaszewski@...are.pl>
Cc:     Wei Wang <weiwan@...gle.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        edumazet@...gle.com
Subject: Re: Latest net-next from GIT panic

On Wed, 2017-09-20 at 06:34 -0700, Eric Dumazet wrote:
> Could you try this debug patch ?
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index f535779d9dc1dfe36934c2abba4e43d053ac5d6f..1eaa3553a724dc8c048f67b556337072d5addc82 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -3331,7 +3331,14 @@ void netdev_run_todo(void);
>   */
>  static inline void dev_put(struct net_device *dev)
>  {
> -	this_cpu_dec(*dev->pcpu_refcnt);
> +	int __percpu *pref = READ_ONCE(dev->pcpu_refcnt);
> +
> +	if (!pref) {
> +		pr_err("no pcpu_refcnt on dev %p(%s) state %d dismantle %d\n",
> +		       dev, dev->name, dev->reg_state, dev->dismantle);
> +		BUG();
> +	}
> +	this_cpu_dec(*pref);
>  }
>  
>  /**
> 

And since the console will be filled by stack trace, maybe instead of
BUG() use some infinite loop ?

for (;;)
	cpu_relax();